Technical Abstract:
Much of current efforts to improve efficiency in cattle use measures of individual feed intake in combination with weight gain as an indication of efficiency. This approach provides pertinent information concerning efficiency during the growing phase, but the relationship to cow efficiency remains to be determined. Efficiency in grazing cows is much more complex, especially when considering input and output traits associated with efficiency as functions of genetics and environmental factors, and interactions of these factors. The most critical output influencing efficiency of beef cattle production is reproductive rate, which is a cumulative process requiring years to establish. Nutrition and management components of environment are more complex in range settings and subject to greater seasonal and annual variation than in confined settings relying solely on harvested feed with greater homogeneity. Methods to measure feed intake while grazing under range conditions are lacking. Seasonal and annual variations in quantity and quality of forage can result in greater distinctions between biological and economic efficiency in the cow-calf phase compared to other segments. For example, cows that consume more calories during the growing season and gain sufficient weight to exist on less harvested feed inputs during winter may require less total economic input than cows with greater biological efficiency that consume less during the growing season, but require more calories from harvested feed later. Efficiency of beef cattle production requires a balance between nutritional inputs and prolonged optimal output. A provocative question to consider is whether traditional approaches of providing sufficient feed to a herd of cows to achieve a relative high rate of reproduction results in improved efficiency or not? Is this analogous to selecting a type of cattle and managing the environment to sustain the type? What happens when cattle are managed corresponding to restriction imposed by a limited environment and provided relatively minimal inputs rather than fed for a desired level of production associated with a resource rich environment?